Both the USSR and PRC inherited the ashes of empire. They didn't cause revolution, they were just there when there was no option but something different. The Bolsheviks and Maoists had the most disciplined power structures to replace it with something that promised/met the basic needs of the people.
I think PSL has the best chance at succeeding for the same reason I think the 1960s/70s Black Panthers had the clearest path to revolution. Their Marxist-Leninist framework means they can build coherent dual structures. When nobody can afford soup, they can run an organised soup kitchen while my local Food Not Bombs is a clusterfuck full of clique drama. They're the org that encourages reading the most books and they have the most formal processes to avoid the pitfalls of non-hierarchical mass movements like Occupy or BLM. In their absence I think DSA has the same basic role, but their ideological murkiness creates a lot more internal tension and their entryist membership is a big security risk.
